Slow DSL (Yet another one....)

Question

I have been in contact with Verizon (via off shore support on their 'tech support line') over the past few months and I have YET to get this issue resolved. Since mid-summer 2010 I have been getting 1.6 meg or so speeds on my 3meg DSL line. Prior to that period I was getting 2.5 meg +. I have called in numerous times and I keep getting told they will perform a line test.... Well, the line is FINE it's my download speed that's hosed. My upload is the correct speed of 728 but for some reason my download speed has been slashed from 2.5 to ~1.5.
Verizon even sent me a new modem as my old westtel was from 2001 and it had no better, (perhaps even slightly slower!!!), speed results on JUST the download side.
Other Verizon DSL users suggest that there is some sort of bandwidth throttling or "error correcting" processes that can cause this sort of thing. I live right around 6,000ft or so from the switching station so I'm WELL within range to get the full benefit from my speed. No lines have changed inside the house in years, yet there is a decrease in speed none the less. I have tried various speed test sites, various combinations of network hardware between the PC and the router and nothing helps.
To make matters worse I called in last week and spoke to another off shore "tech" (script reader more like it), and after cutting him off from trying to walk me through a ton of useless steps that I've gone through about 4 dozen times already and telling him NOT to send out yet ANOTHER modem, had this gentleman tell me that he needed to work with the local dispatch center but it was closed. He arranged to call back the next day between 5 and 7 PM EST with them on the phone to further trouble shoot and get the problem solved. Fine. However, next day, I didn't receive a call back until almost 8:45PM .... AND he started the call off by asking, "So is your problem resolved?" ...... I promptly, and with as much patience as I could muster, told him, "Um, not unless you have done something to FIX it in the time since I last spoke to you..." ... To which he responded by starting the ENTIRE trouble shooting process over again and wanting to run a LINE TEST (which would have raised the count on JUST this one ticket to like 5 or 6!). I cut him off and told him we'd already DONE all that and he was SUPPOSED to call me back at 5:00 not 8:00 with someone from the dispatch so we could sort the problem out! He then told me the dispatch was closed and he'd have to call me back the next day between 3:00 and 5:00 PM EST with a supervisor tech on the line to help diagnose the issue.... That was last Friday... A week later and I still haven't heard from Verizon support.... So first time he was 3hours and 45 minutes late, the second time he was over a WEEK late!
At this point I'm fed up, yet I'm hoping that by posting this here someone MAY be able to help me and FINALLY restore my 3Meg DSL to it's former speed.

Answer 1

I have a LinkSys WRT 310N router between my internal network and the router or I'd pull you the transponder data. As for the other info you asked for: It's a Westel modem, and it's Windows 7 x64... Though every system in my home has the same speed results regardless of OS. Even if I remove the router and connect using the built in PPPoE connection in Windows I get the same speeds, so it's not OS or router related. The modem is a new modem, my old Westtel Wirespeed gave exactly the same results as the brand new westtel modem, so it's not the modem either unless BOTH are bad.
****EDIT****
I found a transponder log I'd taken when I first got the new westtel setup and posted on another forum:
Transceiver Revision: 3.3.6.10.0.1
Vendor ID Code: 4D54
Line Mode: ADSL_2plus
Data Path: Interleaved
DSL Speed: 2112 down and 860 Up
Margin (dB): 12.0 and 10.3
Line Attenuation (dB): 33.1 and 15.0
Transmit Power (dBm): 17.9 and 12.2